The invention relates to polyamide polymers reinforced with silanized glass fibers and produced by means of the activated anionic polymerization of lactams. The invention also includes the actual glass fibers themselves and methods for the production of the fibers.
Thermoplastic material is being increasingly used for the production of construction parts made from fiber-reinforced plastics. The advantage of these plastics over duroplastic material resides primarily in a greater impact resistance and in a relatively good capacity for being reworked.
For reasons of cost, primarily glass fibers in very different forms and amounts are worked in. If possible, the boundary surface bonds between the inorganic fibrous material and the organic matrix material should take place via a chemical reaction. To this end, primarily monomeric silicon compounds, such as silanes, are used as adhesive agents.
Glass fiber products treated with primary amino silanes as adhesive agents are generally available for use with polyamides. However, the use of such glass fibers treated with amino silanes is only suitable for the reinforcement of polyamides (PA) obtained by means of hydrolytic polymerization. Problems frequently occur if fibers silanized in this manner are used in PA construction parts or PA prepregs produced by means of activated anionic polymerization. On the one hand, the activated anionic polymerization of lactams is very moisture-sensitive, and on the other hand, the hydrophilic behavior of the glass filaments is increased even more by the hydrophilic amino silane. Fibers pretreated in this manner must be strictly protected from moisture during storage and processing. So much water is adsorbed on the fiber surface, even at average air moisture, that the polymerization on the fiber boundary surface takes place in an incomplete fashion. The result is that the unreacted, remaining monomer components disturb the bridge formation of the glass fiber-adhesive agent-polymer matrix. Hollow spaces then result around the fibers on account of the relatively high polymerization shrinkage or contraction, such that no strengthening effect can take place in those areas. The fibers no longer exhibit a reinforcing action, but rather a weakening action, since bubbles or shrinkage cavities form. The use of untreated or desilanized fibers does not offer any solution to this problem.
Thus, there is the problem of making an adhesive agent available which exhibits both a bridge-building action as well as a hydrophobing action.